Analysis of the bullet nose of an aero-engine for bird impact through virtual and rapid prototyping

Flying was inspired by birds. But ironically bird strikes are a menace. Therefore, aero-engines have to be designed to survive these strikes. The design of the bullet nose of an aero-engine during a bird strike is presented in this paper. A Finite Element Analysis (FEA) model was developed for this purpose. It was then fine-tuned through experiments on bullet noses built using Laser-Engineered Net-Shaping (LENS). Through this approach, several design alternatives could be evaluated virtually and only a few physical experiments were required for validation. The outcome is not only a rapid and safe bullet nose design but also a realistic FEA model.     

Semi‐theoretical prediction of volumetric mass transfer coefficients in bubble columns with organic liquids at ambient and elevated temperatures

A semi‐theoretical approach for predicting k_La values (referred to liquid volume) in 18 organic liquids [acetone, aniline, 1‐butanol, benzene, cyclohexane, decalin, 1,2‐dichloroethane, 1,4‐dioxane, ethanol (96%), ethylacetate, ethylbenzene, ligroin, methanol, nitrobenzene, 2‐propanol, tetralin, toluene, and xylene] at various operating conditions (including elevated temperatures and pressures) was developed. It was found that the approach is applicable regardless of the hydrodynamic regime (at u_G ≤ 0.1 m/s). Temperatures up to 353 K and pressures up to 0.5 MPa were tested. Two different distributors (multiple‐hole and single‐hole type) were employed. The liquid‐phase mass transfer coefficient k_L was calculated theoretically from the penetration theory on the basis of original definition of gas–liquid contact time. The interfacial area a was defined with respect to the liquid volume. It was found that their product k_La must be multiplied by some correction factor in order to take account of the non‐spherical (ellipsoidal) shape of the bubbles. When the correction term is correlated to both the Eötvös number (Eo) and the dimensionless temperature ratio, 198 experimental k_La values can be fitted reasonably well (average relative error 9.3%).     

用沸点计公式求取γ~∞的适用性

通过用沸点计公式求得的γ∞与其有关文献值的比较及эT／эx2与x2、γ∞2与эT／эx2关系的探讨发现，沸点计法计算γ∞公式对大沸点差特别是沸点差大于50℃的体系不适用.     

The visualization of micro bubble dynamic behavior in capillary microgrooves

Rectangular capillary microgrooves are processed on transparent borosilicate glass. Using high‐speed photography, bubble dynamic behaviors in the microgrooves are observed and analyzed. It is proved that no bubble departs from the bottom of microgroove. The results show that the whole bubble lifecycle can be divided into three distinct stages according to growing velocity. Compared with macroscopic pool boiling phenomenon, bubble life cycle shortens greatly. Experimental results about time‐varying micro bubble sizes are distinctly different from those of theoretical calculation results by the dynamic micro layer model for nucleate pool boiling heat transfer. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; 39(7): 475–481, 2010; Published online 2 June 2010 in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20309     

Wavelet methods for the solution of wave-body problems

Fredholm integral equations of the second kind that arise in wave analysis of floating bodies are solved using a wavelet method. The two-dimensional linear wave-body problem for arrays of rectangular cylinders floating in the free surface of an otherwise unbounded fluid is considered. Both spline wavelets and the Daubechies wavelets with adaption to an interval are used as basis functions. An a priori compression strategy taking into account the singularities of the kernel of the integral equation, which arise at the corners of the geometry, is developed. The algorithm is O(n), where n is the number of unknowns. Computations of the hydrodynamic properties of the cylinders using the compression strategy are performed. The strategy is found to work well. A very high compression rate is obtained, still keeping a high accuracy of the computations. The accuracy of the potential close to the corners (singular points) is examined in a special case where an analytical solution is available.     

Numerical study on mechanism of explosive welding

Abstract

Explosive welding technology has been widely used in industrial production. However, there is always a controversy on the mechanism of explosive bonding, whether explosive welding should belong to a kind of mature welding such as a fusion welding or a solid phase welding. Based on the observation and analysis of the metallographs at interfaces, various opinions are proposed by different authors. This paper investigated the various mechanisms of the wavy interface formation in explosive welding and tried to determine a more reasonable one by using smoothed particle hydrodynamics method. The numerical analysis results show that explosive welding is a unique and complex kind of welding. In general cases, high pressure and melted particles can be found in the collision area at the interface. A version, in which explosive welding is a combination of diffusion bonding, fusion bonding and pressure welding, is considered as a more reasonable one.     

减少连铸板坯开浇气泡的生产实践

结合临钢炼钢连铸的生产实际,对连铸开浇气孔的分布规律、产生原因进行分析,提出了相应的攻关措施。通过采取措施,板坯开浇气泡得到了有效控制。     

提高浇注PBX炸药装药品质技术途径

为提高浇注热固性高聚物粘结炸药(polymer boned explosive,PBX)的品质,对影响高固相含量浇注PBX装药质量的因素进行分析。根据相关理论,运用振动、抽真空及分次装药的方法设计装药工艺参数,通过试验分析不同装药方法排出装药气泡的影响。结果表明：采用真空-振动-分次装药,可有效排出浇注PBX装药气泡,使装药密度提高到98.5%TMD。     

Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred airlift bioreactor

The influence of impeller type in a mechanically stirred airlift bioreactor was analyzed in relation to the non‐Newtonian viscous fluids. The agitation was carried out through a marine impeller (axial impeller) and a paddle impeller (radial impeller) located along with the gas sparger in the region comprised by the riser. The bioreactor was sparged with air under different velocities (0.036–0.060 m s^?1). Carboxymethylcellulose 1.94% and xanthan 1.80% were used as a fluid model. The gas holdup and volumetric mass‐transfer coefficient increased in up to five and three times, respectively, when compared to a conventional airlift bioreactor; however, better results were obtained when the straight paddle impeller type was used. The results suggest that the studied bioreactor can be used successfully in viscous fluid, and it can be more efficient than conventional airlift bioreactors. The results obtained suggest the use of radial impellers. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3159–3171, 2015